It is proposed that a series of para-substituted phenyl glyoxal-bis (4-methyl-3-thiosemicarbazone) copper and zinc chelates be prepared. These chelates will be tested for their ability to inhibit the respiration of rat liver slices and of Ehrlich ascites tumor cells. The chelate structures will be correlated with their biological effect on the two systems by computerized multiparameter regression analysis. The results will be interpreted in terms of possible mechanism of action and in terms of the physico-chemical properties of the chelates which effect potency.